1. Field of the Invention
The present invention relates to a light-emitting diode (LED), and more particularly, to a light-emitting diode (LED) chip for a backlight unit, a manufacturing method thereof, and a liquid crystal display (LCD) device including the same.
2. Discussion of the Related Art
Light-emitting diodes (LEDs) have been widely used as a light source because of small size, low power consumption, and high reliability.
LEDs are formed of III-V semiconductor compounds. In general, LEDs emitting red, green or yellow light are formed of III-V semiconductor compounds, which include arsenide (As) or phosphide (P) as an element of group V, such as aluminum gallium arsenide (AlGaAs), gallium aluminum phosphide (GaAlP), gallium phosphide (GaP) or indium gallium aluminum phosphide (InGaAlP). LEDs emitting green or blue light are formed of III-V semiconductor compounds such as gallium nitride (GaN).
FIG. 1 is a schematic view illustrating an LED chip according to the related art.
In FIG. 1, an LED chip 37 includes a substrate 21, a buffer layer 23, an n-type semiconductor layer 25, a light-emitting layer 27, and a p-type semiconductor layer 29. The LED chip 37 further includes an n-type electrode 35, a p-type electrode 33, and a transparent electrode 31. The n-type electrode 35 is formed on the n-type semiconductor layer 25 partially removing the p-type semiconductor layer 29, the light-emitting layer 27 and a portion of the n-type semiconductor layer 25. The transparent electrode 31 is disposed on the p-type semiconductor layer 29, and the p-type electrode 33 is formed on the transparent electrode 31. The n-type electrode 35 and the p-type electrode 33 provide carriers to the n-type semiconductor layer 25 and the p-type semiconductor layer 29, respectively.
When a forward bias is applied to the n-type electrode 35 and the p-type electrode 33, electrons and holes are transmitted into the light-emitting layer 27 via the n-type semiconductor layer 25 and the p-type semiconductor layer 29, and the electrons recombine with the holes, thereby emitting light.
LED lamps including such an LED chip have been widely used for outdoor advertising bulletin boards or as a backlight source for liquid crystal display (LCD) devices, which are not self-luminous and require an additional light source.
The light emitted from the LED chip 37 is a natural light including light having various polarizations that have different vibration planes for its electric fields.
When such an LED chip is used for devices that use a polarized light with a polarizer such as LCD devices, only about 50% of the light emitted from the LED chip 37 passes through the polarizer. Moreover, the light passing through the polarizer is partially absorbed or reflected while passing through other layers, such as a liquid crystal layer or insulating layers. Accordingly, there is a loss of light, and the brightness of the devices is reduced. Also, increasing the brightness of the devices results in a high power consumption.